function check_login(obj) {
    if (obj.user.value.length <= 0) {
	  alert ("喔！您忘了填寫帳號。\n");
	  obj.user.focus();
	  return false;
    }


    for(var idx=0;idx<obj.user.value.length;idx++) {
	  if (!((obj.user.value.charAt(idx)>= 'a' && obj.user.value.charAt(idx) <= 'z') || (obj.user.value.charAt(idx)>= 'A' && obj.user.value.charAt(idx) <= 'Z') || (obj.user.value.charAt(idx)>= '0' && obj.user.value.charAt(idx) <= '9') || (obj.user.value.charAt(idx) == '_'))) {
	    alert ("帳號不得有特殊符號。\n");
	    obj.user.focus();
	    return false;
	  }
    }

    if (obj.password.value.length <= 0) {
	  alert ("密碼不得空白。\n");
	  obj.password.focus();
	  return false;
    }

    for (var idx=0;idx<obj.password.value.length;idx++) {
	  if(obj.password.value.charAt(idx) == ' ' || obj.password.value.charAt(idx) == '\"' || obj.password.value.charAt(idx) == '\'' || obj.password.value.charAt(idx) == '\\') {
	    alert ("密碼不可以含有特殊符號。\n");
	    obj.password.focus();
	    return false;
	  }
    }
	
  }